Small dogs evolved from Middle Eastern wolves

Genetic studies show that small dogs probably originated in the Middle East more than 12,000 years ago as a result of the domestication of grey wolves, say researchers.

Melissa Gray and Robert Wayne, from the University of California, Los Angeles (USA), led a team of researchers studying variations of the insulin-like growth factor 1 (IGF1) gene.

In a sample of small dogs from many different places around the world, the researchers found the same mutation in the gene at two specific points, which was mainly absent from larger breeds. The research, published in the journal BMC Biology, found that mutations in this gene had a large effect on the skeletal size of dog breeds.

"The most likely scenario is that the mutation which gave rise to small body size arose in the Middle East prior to geographic dispersal of early domestic dogs, which was then selected for and spread with humans as they moved across the continent," said Gray.

The presence of the mutated gene across all small dogs suggests that it developed early in the history of their domestication.

The researchers collected samples from grey wolves from different places around the world, including Alaska, China, Iran, Israel, Italy and Spain. They compared gene clusters from these strains with those of different dog breeds to study the ancestry links. After reviewing information from complete DNA sequencing, they found a close affinity between the genetic clusters of small dogs and those of Middle Eastern grey wolves.

Gray went on to explain that the version of the IGF1 gene found in small dogs is closely related to that found in Middle Eastern grey wolves. This suggests that domestication of grey wolves in this region in densely packed farms could have led to the evolution of small dogs, which might have been preferred by farmers due to the limited farming space available. "The exact steps of the transition from grey wolf to domestic dogs are still under investigation," said Gray.

"Reduction in size is a common event that occurs during the process of domestication," she added. It can be seen in other domesticated animals, such as cattle, pigs and goats.

Although IGF1 has the strongest effect on size, Gray stressed that there are other genes involved. The team chose to start research on this gene because it exhibited the largest effect.

Archaeological work has found the earliest fossils of domesticated small dogs in the Middle East, dating back to 12,000 years ago. Older remains, dating back as far as 31,000 years ago, have been found in Belgium, Germany and Western Russia. However, these remains are of bigger dogs.

This supports the researchers' hypothesis that small dogs originated in the Middle East.